Opening method for packaging bag with fastener

ABSTRACT

An opening method for a packaging bag with a fastener enables the fastener to be surely opened with a simplified arrangement and by a simple operation as compared to the prior art. A packaging bag with a fastener is held by being gripped at the laterally opposite side edges thereof with a pair of grippers. A pair of suction cups are disposed at respective stand-by positions at both sides of the bag. The suction cups are moved to respective mutually close positions and allowed to adhere to both side surfaces of the bag at respective regions where the fastener is present. The suction cups adhering to the bag are retracted to respective intermediate positions. The movement of the suction cups between the mutually close positions and the intermediate positions is repeated a plurality of times. Thereafter, the suction cups are returned to the stand-by positions. The fastener is opened stepwise.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an opening method for opening afastener of a packaging bag (hereinafter, a packaging bag with afastener will be occasionally referred to as a “zippered packagingbag”). More particularly, the present invention relates to a packagingbag opening method suitable for use in an apparatus that performsautomatic packaging of food or the like while moving a packaging bag bygripping the laterally opposite side edges thereof with a pair ofgrippers, wherein a zippered bag is used as the packaging bag.

2. Discussion of Related Art

There has been used a zippered bag whose mouth is closable by fittingengagement between a rib and an associated groove that constitute afastener. More specifically, the rib is formed to extend in the widthdirection on one of the inner surfaces of the opposite walls of the bagnear the upper edge thereof. The groove is formed to extend widthwise onthe other of the inner surfaces of the bag walls. The zippered bag isusable in automatic packaging of food or the like. When the zippered bagis used, it has to be opened before filling of food. A variety ofapparatus and methods for opening the zippered bag have been proposed.

Japanese Patent No. 3429872 discloses an opening apparatus for apackaging bag with a fastener. In this apparatus, first, suction cupsare operated to act on both side surfaces of the bag at respectivepositions above the fastener to open the part of the bag above thefastener. Then, the upper edges of the opposite walls of the opened partof the bag are gripped with grippers, respectively, and the grippers arerotated in opposite directions to each other about their own axes,thereby partially opening the fastener. Thereafter, the grippers aremoved away from each other to fully open the fastener, thereby openingthe bag. In this case, the apparatus requires, in addition to suctioncups, grippers that are capable of opening and closing, and mechanismsfor rotating the grippers or moving them toward or away from each other.Thus, the apparatus has a complicated structure and suffers increasedcosts. In addition, it takes a great deal of time to carry outmaintenance or cleaning works. Because the upper edges of the bag aregripped and pulled with the grippers, the bag mouth may be damaged,causing the appearance of the bag to be degraded.

Japanese Patent Application Unexamined Publication (KOKAI) No. Hei8-104308 discloses a fastener opening apparatus for a packaging bag witha fastener. The apparatus includes a set of driving and driven rollersdisposed at both sides of a bag to be opened. The driving and drivenrollers have their axes extending perpendicular to the extendingdirection of the bag fastener. The rotation of the driven roller isforcedly checked at a certain position against the rotation of thedriving roller, thereby causing the opposite walls of the bag to sliderelative to each other at the fastener part of the bag, and thuspartially disengaging the male and female fastener elements from eachother. This apparatus, however, only provides an automated fasteneropening operation, which has heretofore been carried out by a manualoperation, and is capable of opening the fastener only partially. Tofully open the bag, a device for this purpose is needed separately.Therefore, the apparatus is difficult to apply to an automatic packagingmachine. The arrangement of the apparatus will become extremelycomplicated if it is adapted to be applicable to an automatic packagingmachine. In addition, because the fastener part of the bag is pressedfrom both sides to cause the opposite bag walls to slide relative toeach other, the bag mouth is likely to be deformed, i.e. wrinkled orelongated, or damaged.

Japanese Patent Application Unexamined Publication (KOKAI) No. Hei10-81313 discloses an opening apparatus for a bag with a fastener. Withthe apparatus, suction cups adhering to the opposite side walls of a bagto be opened are rotated about their own axes at respective presentpositions to open a part of the bag above the fastener. Then, thesuction cups are retracted to pull the side walls of the bag. Meanwhile,a nozzle is lowered into the open part of the bag while injectingpneumatic pressure thereinto. Thus, the push-down force of the nozzleand the compressed air pressure are applied to open the fastener. Theoperation of the suction cups takes place in two steps. In addition, theapparatus uses the nozzle device. Therefore, the arrangement iscomplicated. Further, the bag may be deformed or damaged by forcing ofthe nozzle into the bag.

Japanese Patent No. 3578924 discloses a method and apparatus for openinga fastener at the mouth of a bag. The apparatus is arranged as follows.After suction cups have been made to adhere to the opposite side wallsof a bag, a frame rotatably supporting one of the suction cups islowered to move the suction cup downward while tilting it, therebyturning over one side wall at the mouth of the bag to disengage thefastener. Thus, the arrangement is complicated.

Japanese Patent Application Unexamined Publication (KOKAI) No.2004-17985 discloses an opening apparatus for a bag with a fastener. Theapparatus uses a pair of vacuum cups having different configurationsfrom each other. One of the vacuum cups is provided with atrumpet-shaped recess. The other vacuum cup is provided with a rib sothat the cup has a flat suction-adhering surface. The cups each have aflat suction-adhering surface. A bag to be opened is held in such amanner that the male profile side of the fastener faces the cup havingthe recess, whereby the male profile side of the fastener is partiallydistorted during suction, thereby disengaging a part of the fastener. Inthis arrangement, suction cups used in a pair are different inconfiguration from each other. Accordingly, the apparatus cannotfunction as desired if the bag is held in reverse orientation to that inwhich the bag is supposed to be held, in terms of the front and backfaces.

The above-described conventional apparatus are all complicated inarrangement, which causes problems in terms of maintenance and cleaning,or problems in application to an automatic packaging machine. Thedifference in structure between a pair of suction cups used in theconventional apparatus presents a problem that the bag opening operationcannot be performed independently of the orientation of the bag to beopened. The above-described prior art is arranged to open the fastenerin one step of opening operation. Particularly, the apparatus disclosedin the last four of the above-described patent documents use frictionalforce between the rollers and the bag walls, the adhering force of thesuction cups, or pneumatic pressure from the nozzle to open thefastener. Therefore, the force for opening the fastener cannot be saidto be sufficiently strong. If the engaging force between the male andfemale fastener elements is strong, the apparatus may fail to open thefastener.

SUMMARY OF THE INVENTION

The present invention was made in view of the above-described problemsassociated with the prior art.

Accordingly, an object of the present invention is to provide an openingmethod for a packaging bag with a fastener that can open the bag moreeasily and surely than by the prior art method with a simplifiedarrangement. That is, the present invention is based on the knowledgethe present inventor obtained in the process of carrying out researchand development that a packaging bag with a fastener can be opened moreeasily and surely by repeating a simple opening operation a plurality oftimes to thereby carry out the opening process stepwise than by openingthe bag in one step of opening operation.

To attain the above-described object, the present invention provides amethod of opening a packaging bag with a fastener that is gripped atlaterally opposite side edges thereof with a pair of grippers by using apair of suction-adhering members disposed at both sides of the packagingbag. The suction-adhering members are moved to perform a reciprocatingoperation a plurality of times. The reciprocating operation includes aseries of operations of moving the suction-adhering members toward eachother, making the suction-adhering members adhere to both side surfacesof the packaging bag at respective regions where the fastener ispresent, and moving the suction-adhering members adhering to thepackaging bag away from each other. With this method, the process ofopening the fastener proceeds gradually, and the fastener can be easilyand surely opened.

In one embodiment, before starting the reciprocating operation, thesuction-adhering members are placed at respective stand-by positionsapart from each other by a predetermined distance. When moved away fromeach other during the reciprocating operation, the suction-adheringmembers are moved to respective intermediate positions where they arecloser to each other than at the stand-by positions, except for thefinal cycle of the reciprocating operation, which is repeated aplurality of times. This arrangement makes it possible to shorten thestroke of the reciprocating operation and to improve throughputcapability.

In another embodiment, the reciprocating operation is repeated at leastthree times. By repeating the reciprocating operation at least threetimes, presently used general zippered packaging bags can be surelyopened, and the bag opening operation is stabilized.

In still another embodiment, the pair of suction-adhering members arepositioned so that the respective centers of suction-adhering surfacesof the suction-adhering members are displaced relative to each other inthe longitudinal direction of the fastener. If the suction-adheringsurfaces adhere to both side surfaces of the bag in a state where thefastener is closed and the opposite side walls of the bag adhere to eachother in such a way that the suction-adhering surfaces are superimposedover one another, a negative pressure is created in the bag. Thenegative pressure acts to reduce the suction-holding force when thesuction-adhering members move away from each other. By adopting theabove-described arrangement, however, the reduction of thesuction-holding force can be minimized.

In a further embodiment, the suction-adhering members are capable ofreturnably tilting within a plane perpendicular to the side surfaces ofthe packaging bag and containing the fastener. When performing thetilting operation, the suction-adhering members apply a massage-likeaction to the portions of the bag to which they are adhering so as toloosen the fastener, thereby promoting disengagement of the male andfemale fastener elements.

In a still further embodiment, the suction-adhering members are urgedtoward respective predetermined positions with predetermined postures byrespective resilient members, and when the suction-adhering members haveperformed the tilting operation, they are returned by the resilientmembers. With this arrangement, the positions and postures of thesuction-adhering members when adhering to the bag are kept constant andstabilized, and the bag opening operation becomes stabilized.

In a still further embodiment, the suction-adhering members are disposedso that their respective suction-adhering surfaces face obliquelyupward. With this arrangement, when the suction-adhering members adhereto the bag, the mouth at the upper edge of the bag is always opened.Accordingly, once the fastener has been opened, even partially, air canimmediately flow into the bag, whereby the following fastener openingand bag opening operations are facilitated.

According to the present invention, a packaging bag with a fastener canbe opened simply by moving a pair of suction-adhering members to performthe above-described reciprocating operation. Therefore, an apparatus forcarrying out the opening method is extremely simplified in arrangement.The opening operation can be accomplished simply by repeating thereciprocating operation of the suction-adhering members a plurality oftimes. Accordingly, the opening operation can be performed extremelyeasily, simply and surely. Further, the process of opening the bag iscarried out stepwise by repeating the reciprocating operation aplurality of times, unlike the conventional practice of opening the bagin only one step of opening operation. Therefore, the bag can be surelyopened. Once a part of the fastener has been opened, the rest of it canbe opened very easily. Because the arrangement of the apparatus issimplified, the apparatus is excellent in maintainability, cleanability,and so forth.

Other objects and advantages of the present invention will becomeapparent from the following detailed description of illustratedembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the conceptual arrangement of anautomatic packaging machine for carrying out a bag opening methodaccording to a first embodiment of the present invention.

FIGS. 2 a and 2 b are partially-sectioned plan and side views,respectively, showing suction cups at their respective stand-bypositions.

FIGS. 3 a and 3 b are partially-sectioned plan and side views,respectively, showing the suction cups that have advanced to theirrespective positions where they adhere to a bag to be opened.

FIGS. 4 a and 4 b are partially-sectioned plan and side views,respectively, showing the suction cups that have advanced to theirrespective final, mutually close positions.

FIGS. 5 a and 5 b are partially-sectioned plan and side views,respectively, showing the suction cups that have returned to theirrespective intermediate positions.

FIGS. 6 a and 6 b are partially-sectioned plan and side views,respectively, showing the suction cups that have advanced to theirmutually close positions again.

FIGS. 7 a and 7 b are partially-sectioned plan and side views,respectively, showing the suction cups that have returned to theirrespective intermediate positions again.

FIGS. 8 a and 8 b are partially-sectioned plan and side views,respectively, showing the suction cups that have returned to theirrespective stand-by positions after completion of opening the bag.

FIGS. 9 a and 9 b are diagrams showing an essential part of an apparatusfor carrying out a second embodiment of the present invention, in whichFIG. 9 a shows suction cups at their respective stand-by positions, andFIG. 9 b shows the suction cups at their mutually close positions.

FIG. 10 is a diagram showing a part of a bag opening process accordingto a third embodiment of the present invention.

FIG. 11 is a diagram showing another part of the bag opening processaccording to the third embodiment of the present invention.

FIG. 12 is a diagram showing another part of the bag opening processaccording to the third embodiment of the present invention.

FIG. 13 is a diagram showing another part of the bag opening processaccording to the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the accompanying drawings. It should be noted, however,that the following embodiments are for illustrative purposes only, andthat the scope of the present invention is not limited to theseembodiments.

FIG. 1 is a perspective view conceptually showing an automatic packagingmachine for food that employs an opening method for a packaging bag witha fastener according to one embodiment of the present invention. In thefigure, a turntable 2 is secured to a rotating shaft 3 driven by adriving device (not shown) so that the turntable 2 is rotatable togetherwith the rotating shaft 3 as one unit. In this embodiment, the turntable2 rotates intermittently in the direction indicated by the arrow in thefigure. A pair of grippers 5 are disposed underneath the turntable 2near the outer periphery thereof with a predetermined spacing in thecircumferential direction to grip the laterally opposite side edges of abag 4. The grippers 5 receive the bag 4 supplied from the outside of theturntable 2 and move it in a vertically held position to various stepssuccessively to perform operations such as opening the bag, filling thebag with contents, sealing the bag mouth, and discharging the finishedproduct. For these operations or arrangements therefor, publicly knowntechniques can be used satisfactorily, except a bag opening apparatus(described later). Therefore, a detailed description thereof is omitted.The arrangement for securing the grippers 5 to the turntable 2 and theoperation thereof are also publicly known; therefore, a detaileddescription thereof is omitted.

Suction cups 6 and 7 serving as suction-adhering members are secured torespective arms 8 and 9 and disposed facing each other across the bag 4.The way in which the suction cups 6 and 7 are secured to the arms 8 and9 and the operation of the suction cups 6 and 7 will be detailed later.A driving mechanism 11 for operating the arms 8 and 9 will be explainedfirst. It should be noted the driving mechanism 11 is not necessarilylimited to the one that is arranged as stated below, but any drivingmechanism capable of driving the suction cups 6 and 7 to perform anoperation that will be described later.

A cam 12 is secured to a cam shaft 13 driven to rotate by a drivingdevice (not shown) so that the cam 12 rotates together with the camshaft 13 as one unit. A cam lever 14 is secured to a lever shaft 16rotatably supported appropriately so that the cam lever 14 pivotstogether with the lever shaft 16 as one unit. The cam lever 14 rotatablysupports a cam roller 15 at a longitudinally intermediate positionthereon. One end of a return spring 17, which is a tension coil spring,is attached to the distal end of the cam lever 14. The other end of thespring 17 is attached to a spring hook 18 secured to a frame (notshown). Accordingly, the cam lever 14 is constantly urged in a directionin which the cam roller 15 contacts the outer peripheral surface of thecam 12. The outer profile of the cam 12 has the following portions (notdenoted by reference numerals in the figure): a small diameter portionformed over a certain angular range with a small diameter from the axisof the shaft 13; a first displacement portion having a diametergradually increasing from one end of the small diameter portion; a largediameter portion maintaining the length of the diameter at theterminating end of the first displacement portion over a certain angularrange; and a second displacement portion having a diameter graduallydecreasing from the large diameter portion to the other end of the smalldiameter portion.

A hollow stand 19 is stood on the top of a machine base (not shown). Thestand 19 rotatably supports a driving shaft 20. A connecting lever 21 issecured at one end thereof to the lower end of the driving shaft 20 sothat the lever 21 is rotatable together with the driving shaft 20 as oneunit. One end of an air cylinder 22 is pivotably attached to the otherend of the lever 21. The other end of the air cylinder 22 is pivotablyattached to the cam lever 14 at a longitudinally intermediate positionbetween the cam roller 15 and the end thereof to which the spring 17 isattached. The air cylinder 22 is connected to a compressed air source(not shown). Compressed air is supplied into and discharged from the aircylinder 22 under appropriate control, causing a rod 22 a to extend andcontract in response to the supply and discharge of compressed air,thereby moving the suction cups 6 and 7 between their respectivemutually close positions and intermediate positions as explainedhereinafer.

A plate-shaped gear holder 23 is secured to the upper end of the stand19 as shown in the figure. A pinion 24 is positioned in a recess (noreference numeral) formed in an approximately central portion of thegear holder 23 and fixed to the upper end of the driving shaft 20. Racks25 and 26 are disposed and guided in respective slots (no referencenumeral) formed on the gear holder 23. The racks 25 and 26 extendparallel to each other across the pinion 24. As the pinion 24 rotates,the racks 25 and 26 move opposite to each other in their longitudinaldirections. The above-described arms 8 and 9 are integrally secured tothe respective distal ends of the racks 25 and 26. The arms 8 and 9 bothhave an L-shape as shown in the figure. The arm 8 associated with thesuction cup 6 is longer than the other arm 9, so that the suction cups 6and 7 are positioned facing each other across the bag 4 as illustratedin the figure. Piping tubes 27 and 28 are connected to the suction cups6 and 7, respectively. The tubes 27 and 28 are each connected to avacuum pump (not shown) through appropriate members, such as a switchingvalve and a filter (not shown). A nozzle 29 is disposed so that anopening end 29 a thereof is positioned slightly above the upper edge ofthe bag 4. The nozzle 29 injects air to assist in the operation ofopening the bag 4 that is performed by the action of the suction cups 6and 7.

The bag 4 is opened as follows. When the cam roller 15 is on the smalldiameter portion of the rotating cam 12, the suction cups 6 and 7 are atrest at their respective stand-by positions apart from each other. Whenthe bag 4 held by the grippers 5 has moved to and stopped at a bagopening position, the cam roller 15 moves along the first displacementportion toward the large diameter portion in response to the rotation ofthe cam shaft 13. The cam lever 14 moves in the direction of the arrowin the figure, causing the suction cups 6 and 7 to move to theirmutually close positions at which the suction cups 6 and 7 abut againsteach other across the bag 4. A vacuum is applied to the suction cups 6and 7 so that the suction cups 6 and 7 adhere to the outer surfaces ofthe opposite side walls of the bag 4. While the cam roller 15 is movingalong the large diameter portion of the cam 12, the cam lever 14 remainsat the present position. Meanwhile, the air cylinder 22 operates so thatthe suction cups 6 and 7 are returned from the mutually close positionsto respective intermediate positions between the mutually closepositions and the stand-by positions and moved to the mutually closepositions again and then returned to the intermediate positions again.The reciprocating operation of the suction cups 6 and 7 between themutually close positions and the intermediate positions is repeated aplurality of times. When the suction cups 6 and 7 are finally returnedto the mutually close positions, the cam roller 15 is located at the endof the large diameter portion opposite to the leading end thereof. Then,the cam roller 15 moves along the second displacement portion toward thesmall diameter portion. Consequently, the cam lever 14 pivots in adirection opposite to the arrow direction shown in the figure to returnto the previous position. Thus, the suction cups 6 and 7 are alsoreturned to the stand-by positions. While the cam roller 15 is movingalong the small diameter portion of the cam 12, the bag 4 moves to thesubsequent step. The operations of the arms 8 and 9 and the suction cups6 and 7 in this embodiment will be explained below in detail withreference to FIGS. 2 a and 2 b and the following figures.

FIGS. 2 a and 2 b are partially-sectioned plan and side views,respectively, showing the bag 4 having moved to and stopped at the bagopening position and the suction cups 6 and 7, together with the arms 8and 9, at the stand-by positions. The bag 4 is a packaging bag with afastener as stated above. As shown in FIG. 2 b, a fastener 4 a is formedon the inner surfaces of the opposite side walls of the bag 4 at aposition slightly away from the upper edge of the bag 4 to extend in thewidth direction of the bag 4. The fastener 4 a consists essentially of amale fastener element 4 b formed on the inner surface of one side wallof the bag 4 and a female fastener element 4 c formed on the innersurface of the other side wall of the bag 4. The arrangement of thefastener 4 a is publicly known. Therefore, a detailed descriptionthereof is omitted. Regarding the arms 8 and 9, only the bent distal endportions 8 a and 9 a thereof are shown in the figures.

The suction cup 6 has a suction cup body portion 6 a having asuction-adhering surface that is adapted to adhere to the bag 4 bysuction, for which a publicly known arrangement can be employed. Thesuction cup 6 further has a shaft portion 6 b extending rearward fromthe rear end of the body portion 6 a, and a flange 6 c provided at therear end of the shaft portion 6 b to extend radially outward of theshaft portion 6 b. The shaft portion 6 b is fitted in a slot 8 b formedin the bent portion 8 a of the arm 8. The slot 8 b has a predeterminedlength in the width direction of the bag 4. The suction cup 6 is urgedforward, i.e. toward where the bag 4 is positioned, by a compressionspring 10 disposed around the shaft portion 6 b between the body portion6 a and the bent portion 8 a. The suction cup 6 is positioned with theflange 6 c abutting on the bent portion 8 a. In this embodiment, thesuction cup 6 has the shaft portion 6 b abutting on the upper end of theslot 8 b as viewed in FIG. 2 a owing to the way in which the spring 10is installed. It should be noted, however, that the illustratedarrangement of the suction cup 6 is not essential. The arrangement ofthe other suction cup 7 and the way in which it is attached to the bentportion 9 a are the same as in the case of the suction cup 6. Portionsof the suction cup 7 corresponding to those of the suction cup 6 aredenoted by adding the same letters of English alphabet as used for thecorresponding portions of the suction cup 6 to reference numeral 7. Itshould be noted, however, that the shaft portion 7 b abuts on the lowerend of the slot 9 b as viewed in FIG. 2 a.

As shown in FIGS. 2 a and 2 b, the suction cups 6 and 7 stand by atrespective positions at both sides of the bag 4 a predetermined distanceaway from each side of the bag 4 such that the respective centers of thesuction-adhering surfaces 6 d and 7 d face approximately the center ofthe bag 4 in the width direction thereof at substantially the sameposition as the fastener 4 a of the bag 4 in the height directionthereof. As will be clear from FIG. 2 a, however, the suction cups 6 and7 are positioned so that the respective axes are slightly displacedrelative to each other in the width direction of the bag 4. Further, aswill be understood from FIG. 2 b, the suction cups 6 and 7 are disposedso that the respective axes slightly tilt at the same angle to ahorizontal plane and the suction-adhering surfaces 6 d and 7 d faceslightly obliquely upward.

Next, as the cam 12 rotates, the cam roller 15 moves along the firstdisplacement portion, causing the suction cups 6 and 7 to move towardeach other as far as respective positions where the suction cups 6 and 7contact the opposite sides of the bag 4, as shown in FIGS. 3 a and 3 b,as has been stated above. In this embodiment, a vacuum is applied to thesuction cups 6 and 7 slightly before the suction cups 6 and 7 reach theabove-described positions. The vacuum is kept applied to the suctioncups 6 and 7 until completion of a series of opening operations(described later). When the suction cups 6 and 7 are moved to theabove-described positions, because the suction-adhering surfaces 6 d and7 d of the suction cups 6 and 7 face obliquely upward as stated above,the lower portions of the suction cups 6 and 7 abut against each otheracross the bag 4, but the upper portions of the suction cups 6 and 7 areseparate from each other. In this case, however, because the vacuum isacting on the suction cups 6 and 7, side wall portions of the bag 4above the fastener 4 a, at least near where the suction cups 6 and 7 arepositioned, are opened by being sucked to the suction cups 6 and 7, asshown in FIG. 3 b. The inner surfaces of side wall portions of the bag 4below the fastener 4 a also slightly separate from each other, as shownin the figure, owing to the presence of the fastener 4 a in an areawhere the suction-adhering surfaces 6 d and 7 d of the suction cups 6and 7 overlap each other. It should be noted that in this embodiment thecam roller 15 has not yet reached the large diameter portion of the cam12 even when the suction cups 6 and 7 have reach the above-describedpositions.

As the cam 12 rotates further, the cam roller 15 reaches the largediameter portion. Thereupon, the suction cups 6 and 7 assume respectivepositions as shown in FIGS. 4 a and 4 b. That is, when in the positionsshown in FIGS. 3 a and 3 b, the suction cups 6 and 7 have alreadyabutted against each other across the bag 4 at their lower portions andcannot further advance as a whole. The arms 8 and 9, however, furtheradvance against the forces of the springs 10 from the positions shown inFIGS. 3 a and 3 b to the respective positions in FIGS. 4 a and 4 b, thusseparating from the flanges 6 c and 7 c, respectively. Meanwhile, thesuction cups 6 and 7 have their axes displaced relative to each other asstated above, and the shaft portions 6 b and 7 b are respectively fittedin the slots 8 b and 9 b of the arms 8 and 9. Therefore, the shaftportions 6 b and 7 b move within the slots 8 b and 9 b to abut on therespective ends thereof opposite to the above as shown in FIG. 4 a,causing the suction cups 6 and 7 to tilt slightly (the tilting actionmay be regarded as tilting of the suction cups 6 and 7 within a planeperpendicular to the side surfaces of the bag 4 and containing thefastener 4 a). Thus, the suction cups 6 and 7 pinching the fastener 4 aof the bag 4 from both sides shift from the respective positions shownin FIGS. 3 a and 3 b to the positions shown in FIGS. 4 a and 4 b,thereby providing a massage-like action to loosen the fastener 4 a atthe pinched portion. As a result, the fastener 4 a is slightlyelastically deformed. That is, the mouth of the female fastener element4 c widens a little, making it easy for the male fastener element 4 b todisengage from the female fastener element 4 c.

The large diameter portion of the cam 12 is formed to extend over acertain angular range, as has been stated above. While the cam roller 15is moving along the large diameter portion, the following operationtakes place: When the state shown in FIGS. 4 a and 4 b is reached, theabove-described air cylinder 22 is activated at a predetermined timingto withdraw the rod 22 a into the air cylinder 22 by a predeterminedlength. In response to the contraction of the rod 22 a, the pinion 24rotates through a predetermined angle in a direction opposite to theabove, causing the suction cups 6 and 7 to retract to respective.intermediate positions as shown in FIGS. 5 a and 5 b. During theretracting movement to the positions shown in FIGS. 5 a and 5 b, thesuction cups 6 and 7 are adhering to the opposite side walls of the bag4. Thus, the suction cups 6 and 7 pull the bag 4 from both sides thereofand hence act to open the fastener 4 a at the portion thereof where thesuction cups 6 and 7 are adhering. Even if the fastener 4 a is not fullyopened at that portion by the above-described action, the male fastenerelement 4 b begins to disengage from the female fastener element 4 c, asshown in FIGS. 5 a and 5 b. It should be noted that if the suction cups6 and 7 were disposed in such a way that their respective axes coincidewith each other unlike in this embodiment, the following problem mightarise: While the suction cups 6 and 7 are adhering to the bag 4, anegative pressure is created in the bag 4 at the suction-held portionbelow the fastener 4 a. Consequently, when the bag 4 is pulled from bothsides thereof, the pulling force is canceled by the negative pressure,so that the suction holding of the bag 4 by the suction cups 6 and 7becomes incomplete. In such a case, the suction cups 6 and 7 cannot pullthe bag 4 sufficiently and may separate from the bag 4 undesirably. Withthis embodiment, however, a sufficiently strong suction-holding forcecan be maintained.

Next, the air cylinder 22 is activated in reverse to the above to extendthe rod 22 a, causing the suction cups 6 and 7 to assume respectivepositions as shown in FIGS. 6 a and 6 b. More specifically, the suctioncups 6 and 7 move toward the bag 4 again to adhere to the bag 4 andperform the massaging operation to loosen the fastener 4 a, as has beenstated above in connection with FIGS. 4 a and 4 b, to reach therespective positions shown in FIGS. 6 a and 6 b. Then, the rod 22 a ofthe air cylinder 22 contracts again, causing the suction cups 6 and 7 toretract to the intermediate positions again. The air cylinder 22 repeatsthe contacting-extending operation a predetermined number of times whilethe cam roller 15 is moving along the large diameter portion of the cam12. During this operation, a part of the fastener 4 a is fully opened,and the extent of the opening of the fastener 4 a gradually extends asshown in FIG. 7 a. Once a part of the fastener 4 a has been opened, itis easy to open the rest of it. Finally, with the air cylinder 22 keptextended, the cam roller 15 moves along the second displacement portionof the cam 12, causing the suction cups 6 and 7 to return to therespective previous stand-by positions. Thus, the fastener 4 a of thebag 4 is opened over the entire length thereof, and the bag 4 is fullyopened as shown in FIGS. 8 a and 8 b.

It should be noted that air is injected from the nozzle 29 during theabove-described opening operation. As has been stated above, thesuction-adhering surfaces 6 d and 7 d of the suction cups 6 and 7 faceobliquely upward so as to act to open the upper edge portion of the bag4 at all times. Therefore, once the fastener 4 a has been opened, evenpartially, flowing of air injected from the nozzle 29 into the bag 4 ispromoted to facilitate and ensure the opening operation. Eventually, thebag 4 can be fully opened as far as the bottom thereof. It should benoted that, during the above-described operation, the grippers 5gripping the laterally opposite side edges of the bag 4 move toward eachother by a predetermined distance at a predetermined timing so as not tointerfere with the operation of opening the bag 4. The use of the aircylinder 22 makes it possible to adopt an arrangement in which thesuction cups 6 and 7 are not retracted beyond the respectiveintermediate positions except the final retracting operation.Consequently, it is possible to shorten the reciprocating stroke of thesuction cups 6 and 7 and to eliminate useless movement of the suctioncups 6 and 7 and hence possible to improve throughput capability.

FIGS. 9 a and 9 b are diagrams showing a second embodiment of thepresent invention. FIG. 9 a is a plan view corresponding to FIG. 2 a.FIG. 9 b is a plan view corresponding to FIG. 4 a. In this embodiment,suction cups 41 and 42 are secured to respective holders 47 and 48 thatare pivotably supported to arms 43 and 44 (only partially shown) byshafts 45 and 46, respectively. The holders 47 and 48 are subjected toforces from tension springs 49 and 50 retained each at one end thereofby spring retainers 51 and 52, and positioned by abutting on respectivestoppers 53 and 54. The operations of the arms 43 and 44 and the suctioncups 41 and 42 are substantially the same as in the first embodiment. Itshould be noted, however, that the operation of tilting the suction cups41 and 42 as shown in FIG. 9 b is effected by pivoting of the holders 47and 48 about the respective shafts 45 and 46 against the forces of thesprings 49 and 50. The other operations in this embodiment will beunderstood from the description of the first embodiment. Therefore, adescription thereof is omitted. It should be noted that in thisembodiment the suction cups 41 and 42 are placed in predeterminedpositions when retracted. Therefore, the suction cups 41 and 42 cansurely adhere to the same positions on bags, and the opening operationcan be performed stably.

Although in the above-described first and second embodiments the armsand the suction cups move further from the respective positions shown inFIGS. 3 a and 3 b to those shown in FIGS. 4 a and 4 b, it should benoted that the arms and the suction cups may move from the positionsshown in FIGS. 3 a and 3 b directly to the intermediate positions, notmoving to the positions shown in FIGS. 4 a and 4 b, and finally retractto the stand-by positions. That is, the interlocking force of thefastener depends on the arrangement thereof. In a case where theinterlocking force of the fastener is relatively small so that thefastener can be opened without performing the above-described massagingoperation, it is unnecessary to carry out the massaging operation. Inthe first and second embodiments, the fastener opening operation isperformed twice in total. That is, the operation of returning thesuction cups to the respective intermediate positions while pulling thebag from both sides thereof is performed once. In the second suction cupreturning operation, the suction cups are returned to the respectivestand-by positions. The present applicant confirmed that ordinaryzippered packaging bags presently used in automatic packaging can besurely opened by performing the above-described opening operation atleast three times. The number of times of repeating the openingoperation, however, is not necessarily limited to the above but may bedetermined according to the specifications of bags to be used. Whetheror not to perform the massaging operation may also be determinedaccording to need. In the first and second embodiments, the operation ofmoving the suction cups between the mutually close positions and theintermediate positions is performed by using an air cylinder. It is,however, also possible to effect the operation by using the cam itself,for example. If the cam alone is used to perform all the operations ofmoving the suction cups between the stand-by positions and the mutuallyclose positions and moving them between the mutually close positions andthe intermediate positions, however, the cam has to be changed when thenumber of times of repeating the opening operation is changed. In thecase of the foregoing embodiments, however, the number of times ofrepeating the opening operation can be readily changed simply bycontrolling the air cylinder.

In the foregoing first and second embodiments, the table of theautomatic packaging machine intermittently rotates, and theabove-described opening operation is performed while the bag is at restat the first step of the automatic packaging process. Japanese PatentApplication Unexamined Publication (KOKAI) No. 2002-255119, for example,discloses a bag mouth opening apparatus for a bag with no fastener thatis conveyed continuously. It is useful for realizing a high-speedautomatic packaging machine that various operations are performed on abag being moved continuously as disclosed in the JP(A) publication. Thepresent invention is also applicable in a case where a bag with afastener is moved not intermittently but continuously as in theabove-described JP(A) publication. More specifically, in Japanese PatentApplication Unexamined Publication (KOKAI) No. 2002-255119, oneapparatus for opening the bag mouth is provided along the bag conveyingpath. When the present invention is applied to an automatic packagingprocess in which a bag with a fastener is moved continuously, however, aplurality, for example, two, of bag mouth opening apparatuses aredisposed along the bag conveying path. With the plurality ofapparatuses, the opening operation is repeated a plurality of times,whereby a packaging bag with a fastener can be surely opened. Theopening operation will be explained below briefly with reference toFIGS. 10 to 13.

An opening apparatus 71 used in this example may be the same asdisclosed in Japanese Patent Application Unexamined Publication (KOKAI)No. 2002-255119. A pair of suction cups 74 and 75 are disposed facingeach other across a bag 72 held with grippers 73 and moved continuously.The suction cups 74 and 75 are positioned in symmetry with respect tothe travel line (shown by arrows in the figure) of the bag 72. Thesuction cups 74 and 75 rotate in opposite directions to each other abouttheir respective axes 76 and 77 extending perpendicular to the plane ofthe figure. During the rotation of the suction cups 74 and 75, thesuction-adhering surfaces thereof constantly face the bag 72. During themovement of the suction cups 74 and 75, their positions are keptsymmetric with respect to the travel line of the bag 72 at all times. Asecond opening apparatus 81 placed next to the first opening apparatus71 has the same arrangement and performs the same operation as the firstopening apparatus 71.

Numerals shown in the right-top corners in two rectangular frames ineach of FIGS. 10 to 13 indicate the order in which the suction cups 74and 75 move to open the bag 72. Regarding the first apparatus 71, thesuction cups 74 and 75 gradually move toward each other and toward thebag 72 from position “1” to “2” and further to “3” while rotating inopposite directions to each other. At position “4”, the suction cups 74and 75 come closest to each other and abut against each other across thebag 72. Thus, the suction cups 74 and 75 adhere to the respective outersurfaces of the opposite side walls of the bag 72 at the fastener (notshown). It should be noted that the peripheral velocity of the suctioncups 74 and 75 at the positions of the suction-adhering surfaces whenthe suction cups 74 and 75 rotate about their axes 76 and 77 coincideswith the travel speed of the bag 72. Therefore, there is no discrepancybetween the movement of the suction cups 74 and 75 and that of the bag72. Thus, the suction-adhering operation takes place smoothly. Then, thesuction cups 74 and 75 move toward position “5” while continuing torotate and moving away from each other, thereby pulling the bag 72 fromboth sides thereof. When they reach position “6”, the suction cups 74and 75 separate from the bag 72. At this time, a part of the fastenerhas been disengaged or has begun to disengage. Then, the suction cups 74and 75 move from position “7” to “8” where they are remotest from eachother, and then return to position “1”. Meanwhile, the bag 72 that hasbeen treated by the apparatus 71 moves to the position of the secondopening apparatus 81, and a subsequent bag 72 is fed to the position ofthe first apparatus 71. The operation of the second apparatus 81 is thesame as that of the apparatus 71. Therefore, a description thereof isomitted. It should be noted, however, that the fastener has beenpartially opened by the first apparatus 71, or at least a part of thefastener has begun to open. Therefore, the fastener is fully openedeasily and thus the bag 72 is fully opened by the second apparatus 82 asshown at “7” in FIG. 13. In this embodiment also, the fastener openingoperation and hence the bag opening operation can be facilitated andensured effectively by employing the nozzle used in the firstembodiment.

It should be noted that the present invention is not limited to theforegoing embodiments but can be modified in a variety of ways.

1. A method of opening a packaging bag with a fastener that is grippedat laterally opposite side edges thereof with a pair of grippers byusing a pair of suction-adhering members disposed at both sides of saidpackaging bag in such a manner that said suction-adhering members aremoved toward each other so as to adhere to both side surfaces of saidpackaging bag at respective regions where said fastener is present, andsaid suction-adhering members adhering to said packaging bag are movedaway from each other to open said packaging bag, said method comprising:repeating a plurality of times a reciprocating operation including aseries of operations of moving said suction-adhering members toward eachother, making said suction-adhering members adhere to said packagingbag, and moving said suction-adhering members adhering to said packagingbag away from each other.
 2. The method of claim 1, wherein beforestarting said reciprocating operation, said suction-adhering members areplaced at respective stand-by positions apart from each other by apredetermined distance, and when moved away from each other during saidreciprocating operation, said suction-adhering members are moved torespective intermediate positions where they are closer to each otherthan at said stand-by positions, except for a final cycle of saidreciprocating operation, which is repeated said plurality of times. 3.The method of claim 1, wherein said reciprocating operation is repeatedat least three times.
 4. The method of claim 2, wherein saidreciprocating operation is repeated at least three times.
 5. The methodof claim 1, wherein said pair of suction-adhering members are positionedso that respective centers of suction-adhering surfaces of saidsuction-adhering members are displaced relative to each other in alongitudinal direction of said fastener.
 6. The method of claim 5,wherein said suction-adhering members are capable of returnably tiltingwithin a plane perpendicular to the side surfaces of said packaging bagand containing said fastener.
 7. The method of claim 6, wherein saidsuction-adhering members are urged toward respective predeterminedpositions with predetermined postures by respective resilient members,and when said suction-adhering members have performed said tilting, theyare returned by said resilient members.
 8. The method of claim 1,wherein said suction-adhering members are disposed so that theirrespective suction-adhering surfaces face obliquely upward.
 9. Themethod of claim 5, wherein said suction-adhering members are disposed sothat their respective suction-adhering surfaces face obliquely upward.